The core represents the most efficient, cost-effective, reliable source of the required samples, which will range from modified oligonucleotides and larger DNA sequences to mouse skin treated with polycyclic aromatic hydrocarbons (PAH) and mouse papillomas. All of th necessary facilities and expertise for the Core are available in the Eppley Institute. In brief, the Core will provide mouse skin treated with PA, cells from mouse skin treated with PAH, HeLa cells treated with PAH, and mouse skin papillomas induced by PAH. In addition, the Core will provide 18-base pair oligonucleotides either containing an apurinic site or modified with PAH or catechol estrogen quinones (CE-Q) and longer defined DNA sequences modified with PAH or CE-Q. Provision of biological preparations by the Core component will expedite the research conducted in the program project grant. In addition, analysis of split samples by collaborators will enhance quality control and will assure that comparison of results obtained by different methods is valid.